Radiation projector and shielding means



May 10, 1960 F. JENSEN 2,936,378

RADIATION PROJECTOR AND SHIELDING MEANS Filed Sept. 7, 1956 INVENTOR AGENT United States RADIATION PROJECTOR AND SHIELDING MEANS Application September 7, 1956, Serial No. 608,627

5 Claims. (Cl. 250-106) Apparatus are known by means of which natural or artificial radio-activity is employed in therapy. When using radio-active isotopes such as, for example, 60 180 192 137 or the like, the source of radiation is shielded by means of lead, in which use is made of an envelope of lead containing a lead sphere or a tungsten disc arranged for rotation. Both parts comprise a channel for the passage of the radiation and by turning the inner part, its channel is ofiset with respect to the channel of the envelope. During operation, the inner part is so arranged as to form a continuous channel. During stoppages, the axes of the two channels extend substantially at right angles to each other so that radiation to the outside is prevented. Half the diameter of such a device should correspond to at least double the wall-thickness required for stopping the radiation, hence the device requires a considerable quantity of additional material, which adversely afiects both its size and weight.

For this reason, devices have been proposed, in which the thickness of the material surrounding the source of radiation corresponds to the wall-thickness required for stopping the radiation, and in which the channel for the passage of the radiation is closed by means of mercury. On account of its density exceeding that of lead, although it has substantially the same atom number, mercury has better absorption properties.

The weight of a device with a mercury seal is several times as low as that of the device referred to in the preamble. For operating the known irradiation apparatus with a mercury seal, the mercury is expelled, by means of compressed air, from the channel for the passage of the radiation into an upper container, whence the mercury, due to its weight, again drops into the channel for the passage of the rays as soon as the pressure ceases. The use of gravity renders such irradiation apparatus unsuitable for use in positions other than those in which the container is situated above the channel, which is undesirable in therapy.

The present invention has for its purpose to obviate this disadvantage. It concerns irradiation apparatus comprising a radio-active source of radiation, more especially but not exclusively for use in therapy, in which the channel for the passage of the radiation is closed by means of mercury during stoppages and the mercury is expelled from the channel by means of compressed air. According to the invention, provision is made of a displacer which is impelled by the compressed'air, this displacer urging the mercury against the action of a flexible member, for example a helical spring, into a space which is located adjacent the channel for the passage of the radiation and outside the lead screen.

The invention will be described in connection with the agg 2,936,378 Patented May 10, 1960 ice accompanying drawing, the single figure of which shows a radiation projector according to the invention.

A source of radiation 1 is centrally arranged in a spherical lead member 2. A channel 4 serves for the passage of the radiation. This channel contains a thinwalled steel tube 3a which is a close fit in the channel and merges into a wider tube 3 having a double wall and protruding from the member 2. The channel 4 is filled with mercury, hence the source of radiation 1 is sealed to the outside. The seal is removed when a hollow piston 5 made from a material, for example synthetic resin, by which the radiation is only slightly absorbed, is urged by means of compressed air into the channel 4 for the passage of the radiation, said piston urging the mercury there present into the annular widening 3 of the tube 3a, Whilst impelling an annular piston 8 and compressing a helical spring 9. The mercury-filled annular space Within the tube 3 constitutes an applicator, by which the radiation is formed into a beam. After irradiation, the compressed air is allowed to escape from the piston 5 through the channel 10, the helical spring 9 causing, via the piston 8, the mercury in the channel 4 for the passage of the radiation and consequently the piston 5 to resume their initial positions so that the source of radiation is again sealed by the mercury within the tube 3a. Between the displacer 5 and the inner wall of the wider portion 3, provision is made of sealing rings 7, for example of rubber. At its end remote from the source of radiation, the tube 3 is provided with a closure member 6, made from a material for example synthetic resin, in which a channel 10 for the supply and exhaust of compressed air empties.

What is claimed is:

1. An irradiation device comprising a radioactive source of radiation, a lead screen having a channel for the passage of a beam of radiation from said source, a supply of mercury for closing saidchannel and intercepting said beam of radiation, means to expel the mercury from said channel into a chamber located adjacent the channel and outside the lead screen, said mercury expulsion means comprising a displacement member adapted to be impelled by a gaseous medium under pressure, and a flexible member in said chamber for urging the mercury against the action of said displacement member.

2. A device as claimed in claim 1, in which the displacement member is a piston of synthetic resin, which absorbs the radiation only slightly.

3. A device as claimed in claim 1, in which the chamber located adjacent the channel for the passage of the radiation is of annular cross-section and constituted by a double walled tube and said displacement member is an annular piston movable in said chamber which remains in contact with the mercury by the pressure of a spring.

4. A device as claimed in claim 3, in which sealing rings are provided between the displacement member and the inner wall of the double-walled tube.

5. A device as claimed in claim 4, in which the double- Walled tube is sealed with a synthetic resin which absorbs the radiation only slightly and in which a channel is provided for supplying and carrying ott compressed air.

Green Aug. 18, 1953 Stewart et a1. Apr. 13, 1954 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION I Patent No. 2,936,378

May 10 1960 Fritz Jensen It is hereby certified t ent requiring correction and corrected below.

hat error appears in the above numbered patthat the said Letters Patent should read as In the heading to the printed specific lines 8 and 9, insert ation, between aims priority, application Germany September 10, 1955' S1gned and sealed this 25th day of April 1961 (SEAL) Attest: ERNEST W. SWIDER DAVID L. LAD Attesting Officer Commissioner of Patents 

1. AN IRRADIATION DEVICE COMPRISING A RADIOACTIVE SOURCE OF RADIATION, A LEAD SCREEN HAVING A CHANNEL FOR THE PASSAGE OF A BEAM OF RADIATION FROM SAID SOURCE, A SUPPLY OF MERCURY FOR CLOSING SAID CHANNEL AND INTERCEPTING SAID BEAM OF RADIATION, MEANS TO EXPEL THE MERCURY FROM SAID CHANNEL INTO A CHAMBER LOCATED ADJACENT THE CHANNEL AND OUTSIDE THE LEAD SCREEN, SAID MERCURY EXPULSION MEANS COMPRISING A DISPLACEMENT MEMBER ADAPTED TO BE IMPELLED BY A GASEOUS MEDIUM UNDER PRESSURE, AND A FLEXIBLE MEMBER IN SAID CHAMBER FOR URGING THE MERCURY AGAINST THE ACTION OF SAID DISPLACEMENT MEMBER. 